The confusions is around people viewing byte strings implicitly as ascii codepoints, and not fully understanding what the things they're looking at actually are.
output = ''.join(str(x) for x in some_list)
That's maybe because JSON is by the standard supposed to be utf-8, always.
The point of the comment is that everyone knows that you json encode native entities to the utf8 representation, and json decode from utf8 to native entities.
The same is true of unicode. It's not ambiguous at all.
Only utf-8 is a very specific encoding, so converting to it is straightforward, whereas unicode is an umbrella term and the most ambiguous thing you can imagine.
Even saying "the same is true of unicode" shows confusion, as utf-8 is itself unicode. As are numerous different encodings, and then you have normalization and other subtleties.
If some is "in Unicode" it's a list of codepoints - that is the "thing" to be encoded. I don't see that ambiguity. It's a list of numbers, it's not fluffy kittens in the network or something. UTF-8 is a way of transcribing that list of numbers as 1s and 0s. That is the encoding process. Once it's encoded to 1s and 0s, it's not anything. It's just 1s and 0s.
One person's utf8 encoded 1s and 0s may be another person's audio signal. It doesn't really make sense to talk about the encoded data as being utf8. It's the encoded / decoding process that's utf8. Sure, it might be utf8 decodable.
In terms of json, it's the same deal. You have the "thing", simple nested objects/lists/numbers in memory. It only makes sense to talk about json when you're talking about the process of transcribing those.
In both cases you have a "thing" (I think of it as "real", but in a way it's an abstract concept - how does Python represent a dict, I have no idea), you can encode those things into a tangible list of 1s and 0s.
That's why they're the same. And people aren't generally confused about the json encoding decoding process.